Humans naturally acquire the language or languages that they are exposed to in early childhood, but these languages are different from one another and are all the product of historical change over many millennia, much of it resulting from chance. Natural sign languages are social creations that emerge in communities with an acute need to communicate. Many sign languages in Europe and North America developed from the establishment of schools for deaf children through the eighteenth and nineteenth centuries. The study of new sign languages such as Al-Sayyid Bedouin Sign Language (ABSL) offers a real-life view of how a language emerges a new, how it conventionalizes and spreads across users in a community. A fundamental property of human language is the existence of syntax, the level of organization that contains conventions for combining symbolic units, the words. The chapter also discusses lexicons, phonology, morphology, and semantics that characterize language.